Mesoporous Hollow Sphere Titanium Dioxide Photocatalysts through Hydrothermal Silica Etching

Robust, monodisperse, mesoporous titanium dioxide (TiO₂) submicrometer hollow spheres were synthesized through a single step hydrothermal silica etching reaction under mild conditions. Efficient silica (SiO₂) removal was achieved without the use of toxic reagents, and a unique controllable silica redeposition mechanism was identified, imparting the hollow spheres with excellent structural integrity. The parameters of the hydrothermal reaction affecting the etching process, including pH, temperature, and silica concentration, were systematically investigated and optimized for the production of silica-templated hollow structures. The resulting processing conditions yielded TiO₂ hollow spheres with a surface area of ∼300 m² g⁻¹ and anatase phase crystallization, which exhibited high adsorption capacity for methylene blue dye and good photocatalytic activity without requiring high-temperature calcination.